Elastic laminates have previously been used in a variety of disposable products, including sweat bands, bandages, body wraps, and disposable garments including disposable diapers and incontinence devices. Herein, “elastic laminate” refers to an elastically stretchable two or more layered materials including at least one elastically stretchable single layer material. It is generally expected that these products provide good fit to the body and/or skin of the user by using suitable elastic members during the entire use period of products.
A “zero strain” stretch laminate is one type of elastic laminate which is preferably used for such disposable products. For example, methods for making “zero strain” stretch laminate webs are disclosed in U.S. Pat. No. 5,167,897 issued to Weber et al. on Dec. 1, 1992; U.S. Pat. No. 5,156,793 issued to Buell et al. on Oct. 20, 1990; and U.S. Pat. No. 5,143,679 issued to Weber et al. on Sep. 1, 1992. In a manufacturing process for such “zero strain” stretch laminate, the elastomeric material is operatively joined to at least one component material in a substantially untensioned (zero strain) condition. At least a portion of the resultant composite stretch laminate is then subjected to mechanical stretching sufficient to permanently elongate the non-elastic components. The composite stretch laminate is then allowed to return to its substantially untensioned condition. Thus, the elastic laminate is formed into a “zero strain” stretch laminate. Herein, “zero strain” stretch laminate refers to a laminate comprised of at least two plies of material which are secured to one another along at least a portion of their coextensive surfaces while in a substantially untensioned (“zero strain”) condition; one of the plies comprising a material which is stretchable and elastomeric (i.e., will return substantially to its untensioned dimensions after an applied tensile force has been released) and a second ply which is elongatable (but not necessarily elastomeric) so that upon stretching the second ply will be, at least to a degree, permanently elongated so that upon release of the applied tensile forces, it will not fully return to its original undeformed configuration. The resulting stretch laminate is thereby rendered elastically extensible, at least up to the point of initial stretching, in the direction of initial stretching.
As is noted in the above, the manufacturing process of such “zero strain” stretch laminate includes the step of subjecting the non-elastic composite stretch laminate to mechanical stretching sufficient to permanently elongate the non-elastic components. This step is additional to normal elastic lamination processes and gives limitations to materials to be used in the elastic laminate. For example, the elastomeric material and other composite material(s) used in the elastic laminate need to have enough physical strength or toughness since those materials tend to be mechanically damaged by the process. If the elastomeric material, for example, does not have enough strength or toughness, the elastomeric material tends to be easily shred or tom by the stress which is applied to the elastomeric material during the mechanical stretching in the manufacturing process and during the use of products.
Based on the foregoing, there is a need for an elastic laminate that does not have such limitations to the elastomeric material to be used therein.
Infants and other incontinent individuals wear disposable garments such as diapers to receive and contain urine and other body exudates. One type of the disposable garments, which is often called as “tape type”, has a fastener system to hold the disposable garment at the wearer's waist area. As the fastener system, either an adhesive tape system or a mechanical fastener system is often used. Recently, elastically stretchable ear panels tend to be preferably used in this type of disposable garment, because they can provide a better fit to the wearer's waist area by jointly working with the fastener system. Another type of disposable garments, which is often called as “pant type” or “pull-on”, has fixed sides and has become popular for use on children able to walk and often who are toilet training. This type of pull-on garments has ear panels the edges of which are seamed together to form two leg openings and a waist opening. They also has a stretchable waistband disposed along at least one of the end edges of the disposable garments. These pull-on garments need to fit snugly about the waist and legs of the wearer without drooping, sagging or sliding down from position on the torso to contain body exudates. Examples of these pull-on garments are disclosed, for example, in U.S. Pat. No. 5,171,239 to Igaue et al., U.S. Pat. No. 4,610,681 to Strohbeen et al., WO 93/17648 published on Sep. 16, 1993, U.S. Pat. No. 4,940,464 to Van Gompel et al., U.S. Pat. No. 5,246,433 to Hasse et al., and U.S. Pat. No. 5,569,234 to Buell et al.
Good performance characteristics of such stretchable ear panels and waistband are important for these types of disposable garments. More specifically, the extension properties including the extension forces, recovery forces, retention forces, and available stretch (extension) of the ear panels and waistband are important considerations in the performance of the fitness for pull-on garments. The extension properties provide the applicator and the wearer with the overall perceived “stretchiness” during use. They also effect the ability of the applicator to achieve a suitable degree of application stretch (i.e., for a “normally” perceived tensioning of the diaper during application, the total amount of resultant stretch is that desired to achieve/maintain good conformity of fit).
To provide good performance characteristics in stretchable ear panels and waistband of disposable garments, elastic laminates which include an elastic material which has suitable properties have been studied and applied to disposable garments. For example, a PCT application No. PCT/US98/05895 entitled “Elastic Member And Disposable Garment Having Improved Fitness To Body During Entire Use” filed on Mar. 26, 1998, discloses such elastic materials for disposable garments. It is generally expected that disposable garments provide good fit to the body and/or skin of the user by using suitable elastic laminates during the entire use period of products. Typical examples of such elastic laminates that have been previously used include composites formed from an elastic material joined to a non(or less)-elastic material such as nonwoven fabrics and plastic films. These non(or less)-elastic materials tend to affect expected elastic properties of elastic laminates. For example, those materials tend to decrease elastic “stretchiness” of the stretchable ear panels during use.
Based on the foregoing, there is also a need for disposable garments which employ an elastic laminate that does not decrease elastic “stretchiness” thereof.